Science Questions

Why doesn't my watch self-wind when I'm ill?

Thu, 5th Sep 2013

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Adrian van der Werf asked:

My automatic wrist watch is 51 years old, (no manual winding, nor batteries, winds itself by any movement) and is usually worn on my left wrist. The only time this watch stops is occasionally when I am a bit off colour, with a slight temperature, flu or the like.


So, the question is, any idea please why or how this happens?


Many thanks, regards, Adrian van der Werf.






Ginny - Automatic wrist watches are really, really clever. So, you used to have toWrist watch wind a watch because a watch needs energy in order to move the hands around. So, you used to have to wind up a little rotor inside that then drives the hands around. But what these kind of automatic watches have is there's a weighted bit inside that moves every time you move your arm. And you move your arm quite a lot during the day without even noticing it. So, that movement winds the spring that drives the hands. Watches vary in how much energy they can store. Most of them actually, you can take off over night or even if you leave them on, you're not moving over night and they’ll store enough energy to still work perfectly well the next day. So, the only thing I can think here is that if you’ve been ill, you're probably not moving around as much. If you’ve got flu, you might be taking it a bit easy on the sofa. So, even if your watch is on, chances are, you're not moving your arms around quite as much. So, maybe if you're ill for a day, then it’s gone a night and a day, and another night without much winding, that might be enough for it to stop.


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That you are less physically active when unwell, or that you wear the watch less when unwell,
( e.g. spend more time in bed, with the wristwatch lying stationary somewhere ).

There are gadgets which will wind such watches when you're not wearing them ...

or you could replace the cat's collar with the watch and make it earn its keep  RD, Fri, 2nd Aug 2013

Ever see a cat sitting motionless by a hole for hours at a time?

I will say that I also found about a half dozen of the neighbor's cat collars at my house in Portland, usually discovered after they've been out in the weather for some time. CliffordK, Fri, 2nd Aug 2013

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